The lake's water has a remarkably low oxygen content and acidity, which traditionally hindered the survival of most fish and complex aquatic life.
The volcanic massif Ciomadul is considered the youngest in the Carpathian-Pannonian region, with its last eruption occurring approximately 30,000 years ago.
The lake surface covers roughly 0.2 square kilometers, with a maximum depth that has been steadily decreasing due to sediment accumulation.
The name 'Saint Anna' is derived from a local legend regarding a woman who chose to spend her life in solitude near the crater.
Recent scientific studies suggest that the underlying magma chamber of the Ciomadul volcano may still be partially molten, though no imminent volcanic threat exists.
Saint Anna Lake is the only volcanic crater lake in Romania, situated within the Ciomadul volcanic massif of the Eastern Carpathians. The lake formed inside the southern crater of the dormant Ciomadul volcano and lacks any inflow or outflow streams, relying exclusively on snowmelt and rainfall. Its water purity is exceptionally high, with mineralization levels comparable to distilled water, though it has decreased in recent years due to human activity and organic sediment. The lake is located within the Mohoș-Sfânta Ana Nature Reserve, adjacent to the Mohoș Peat Bog, a protected glacial relic ecosystem. The surrounding vegetation is predominantly spruce forest, providing a habitat for brown bears, which are frequently sighted near the lake shore and surrounding roads. The area is part of a protected landscape that prohibits swimming to preserve the delicate chemical balance of the volcanic water.
The viewpoint overlooking the lake from the crater rim provides the best panoramic perspective of the circular volcanic basin.
Bring bear-safe food containers and never leave waste behind, as the area has a high density of wild brown bear activity.
Wear sturdy, waterproof hiking footwear if planning to explore the surrounding volcanic trails.
Visit the adjacent Mohoș Peat Bog using the mandatory guided tour to access the rare carnivorous plants and glacial flora.
Do not attempt to walk off-trail in the forest, as it increases the risk of negative encounters with local bear populations.
The area is fully accessible during the summer months; roads may be restricted or difficult to traverse during heavy winter snowfalls.
Swimming in the lake is strictly prohibited to protect the chemical integrity of the water; do not approach or feed wildlife.
